National survey of Salmonella prevalence in lymph nodes of sows and market hogs

Livestock are known to harbor Salmonella in their gastrointestinal (GI) tract and lymphatic tissues. Pathogens may be transferred from the GI tract to external carcass surfaces during normal harvest procedures but can be mitigated by antimicrobial carcass interventions. Lymph nodes (LNs) are typically encased in fat and are protected from antimicrobial carcass surface treatments, thus serving as a possible root cause of foodborne illnesses attributed to Salmonella in meat products. Members of the pork industry are committed to food safety and want to better understand Salmonella as a potential contaminant in pork products. To establish a baseline of Salmonella prevalence in porcine LNs across the United States, 21 commercial pork harvest facilities, representing northern (n = 12) or southern (n = 9) geographical regions, participated in this study. As processing volumes allowed, 25 carcasses were selected from each establishment. From each carcass, left and right superficial inguinal LNs (n =1,014 LNs) were removed and pooled to yield one sample per animal or n = 507 total LN samples. Salmonella prevalence rates differed (P < 0.05) between hog types in both regions. Specifically, 6.4% of market hog and 37.0% of sow samples were Salmonella positive in the northern region. This was reversed in the southern region as 13.0% of market hog and 4.8% of sow samples were Salmonella positive. There also was a difference (P < 0.05) in prevalence rates between northern and southern regions for sows, but not market hogs (P > 0.05). Type of chilling method (conventional, blast, or other) used at each market hog facility (n = 12) was documented. In the northern region, prevalence rates of Salmonella across chilling types were as follows: 20.0%, 2.7%, and 1.3% positive samples for conventional, other, and blast chill methods, respectively. In the southern region, 20.0% of samples were positive for conventional, 0.0% for blast, and 12.0% for other chilling methods. In both regions, samples from conventionally chilled carcasses returned more (P < 0.05) positive results than any other chill method. Overall, the higher rate of Salmonella prevalence in northern sows warrants further investigation, and members of the pork industry would benefit from the identification of possible methods to address the presence of Salmonella in porcine LNs.

Vitamin D3 supplementation of cull cows: Effects on longissimus and semitendinosus muscle tenderness

Previous studies have shown that supplementation of vitamin D3 to cow diets for 4 to 10 d before slaughter lowers Warner-Bratzler shear force (WBSF) values and increases sensory tenderness scores in beef cuts. The present study was conducted to evaluate the effects of vitamin D3 supplementation on muscle calcium concentration, WBSF values, and sensory tenderness ratings of LM and semitendinosus (ST) muscles from cull, predominately Angus, cows (eight cows per treatment). Treatments included 0 (control), 5 million IU, or 7.5 million IU of vitamin D3 supplemented daily for 7 d preslaughter. Twenty-four hours after slaughter, 2.54-cm-thick LM and ST muscle steaks were cut; aged for either 0, 7, 14, or 21 d (ST steaks aged for 7 d only); and frozen at -20 degrees C for WBFS and sensory analysis. Mean values for LM calcium concentration tended to increase (P = 0.14) with vitamin D3 supplementation (154, 176, and 183 microig/g, fresh basis, for 0, 5, and 7.5 million IU/d, respectively). After 7 d of aging, LM steaks from cows fed 7.5 million IU had lower (P < 0.05) WBSF values than 7-d steaks from controls and cows fed 5.0 million IU/d aged 7 d; however, vitamin D3 supplementation had no (P > 0.05) effect on WBSF values of ST steaks aged 7 d. Vitamin D3 supplementation did not (P > 0.05) affect sensory tenderness ratings for either LM or ST steaks at any aging period. Aging, however, had a linear (P < 0.001) effect on tenderness, with an increase in tenderness as aging time increased from 0 to 21 d. Thus, results from the present study indicate that vitamin D3 supplementation, at these levels and duration before slaughter, provided little benefit to muscle tenderness of beef from cull cows.

Color stability of semitendinosus, semimembranosus, and biceps femoris steaks packaged in a high-oxygen modified atmosphere

The objectives of this study were to evaluate visual and chemical attributes of beefsteaks from various USDA quality grades and muscles packaged in high-oxygen (80% O2/20% CO2) modified-atmosphere packaging (MAP). A total of nine carcasses were selected to represent Select (n = 3), low Choice (n = 3), and high Choice (n = 3) USDA quality grades. The semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF) muscles were removed from each carcass and allotted to two packaging types (MAP or polyvinyl chloride over-wrap) and were displayed for up to 10 d, with evaluation on d 1, 3, 5, 7, and 10. Fifty-four steaks were evaluated on each day by a five-member trained panel for visual color (lean color and discoloration) and were also analyzed with a Minolta Chroma Meter CR-310 for L* and a* values (lightness and redness, respectively). Chemical properties measured included percentage of metmyoglobin formation and fat content. Visual color scores did not differ (P > 0.05) at d 1 and 3 with respect to all quality grades, but decreased after d 3, with a greater reduction (P < 0.05) in high Choice steaks for both lean color and discoloration. The low Choice steaks packaged in MAP displayedhigher (P < 0.05) lean color scores and less (P < 0.05) discoloration at d 7 and 10 than did Select and high Choice steaks. Redness (a*) values also decreased (P < 0.05) after d 3, whereas (lightness) L* values declined (P < 0.05) from d 1 to 5. The high Choice steaks had higher (P < 0.05) metmyoglobin content than low Choice and Select steaks, but packaging had no effect (P > 0.05) on metmyoglobin content. Muscle type did affect metmyoglobin content; however, the metmyoglobin content of the SM was greatest (P < 0.05), followed by the BF, with the ST having the lowest (P < 0.05) metmyoglobin formation. Results indicate that low Choice steaks react the best in MAP, and the ST maintained greater storage characteristics regardless of quality grade or packaging.

Soybean meal from roundup ready or conventional soybeans in diets for growing-finishing swine

Dehulled soybean meal prepared from genetically modified, herbicide (glyphosate)-tolerant Roundup Ready soybeans containing the CP4 EPSPS protein and near-isogenic conventional soybeans were assessed in an experiment with growing-finishing pigs. The soybeans were grown in the yr 2000 under similar agronomic conditions except that the Roundup Ready soybeans were sprayed with Roundup herbicide. Both were processed at the same plant. The composition of the two types of soybeans and the processed soybean meal were similar. Corn-soybean meal diets containing conventional or Roundup Ready soybean meal and fortified with minerals and vitamins were fed to 100 cross-bred pigs from 24 to 111 kg BW. Diets contained approximately 0.95% lysine initially and were reduced to 0.80 and 0.65% lysine when pigs reached 55 and 87 kg BW, respectively. There were 10 pens (five pens of barrows and five pens of gilts) per treatment with five pigs per pen. All pigs were scanned at 107 kg mean BW and all barrows were killed at the end of the test for carcass measurements and tissue collection. Rate and efficiency of weight gain, scanned backfat and longissimus area, and calculated carcass lean percentage were not different (P > 0.05) for pigs fed diets containing conventional or Roundup Ready soybean meal. Gilts gained slower, but they were more efficient and leaner (P < 0.05) than barrows. Responses to the type of soybean meal were similar for the two sexes with no evidence of a diet x sex interaction for any of the traits. In most instances, carcass traits of barrows were similar for the two types of soybean meal. Longissimus muscle samples from barrows fed conventional soybean meal tended (P = 0.06) to have less fat than those fed Roundup Ready soybean meal, but water, protein, and ash were similar. Sensory scores of cooked longissimus muscles were not influenced (P > 0.05) by diet. The results indicate that Roundup Ready soybean meal is essentially equivalent in composition and nutritional value to conventional soybean meal for growing-finishing pigs.

Effects of Acetic-Lactic Acid Treatments Applied to Beef Trim on Populations of Escherichia coli O157:H7 and Listeria monocytogenes in Ground Beef †

The efficacy of organic acid sprays for eliminating Escherichia coli O157:H7 and Listeria monocytogenes from beef trim used in a model ground beef production scheme was determined. Beef trim pieces with ca. 20% fat inoculated with E. coli O157:H7 or L. monocytogenes (ca. 3 log₁₀ CFU/g) were utilized as controls or treated by spraying with 2 or 4% acetic and lactic acids. Propylene glycol (20%) was the carrier for each treatment. Following acid treatment, intact pieces were stored at 4°C for 12 or 24 h, ground, divided into 4 100-g retail packages and stored at 4°C for 0, 1, 2, or 4 days, at which time surviving populations of E. coli O157:H7 or L. monocytogenes were enumerated. High populations (>2.6 log₁₀ CFU/g) of the pathogens persisted in all treatments. The 2% acid spray reduced (P < 0.01) the E. coli O157:H7 population by only 0.1 log₁₀ CFU/g. The 2 and 4% acid sprays reduced (P < 0.001) the L. monocytogenes populations by 0.36 and 0.44 log₁₀ CFU/g, respectively. Storing beef trim intact prior to grinding resulted in lower populations of E. coli O157:H7, and storage following grinding did not affect populations of either pathogen. The acid treatments tested were only slightly effective as sanitizers for beef trim destined for ground beef production.

Use of Organic Acids To Improve the Chemical, Physical, and Microbial Attributes of Beef Strip Loins Stored at -1°C for 112 Days ‡

Twenty-one beef strip loins (Institutional Meat Purchasers Specification #180) were cut into equal halves. One-half of each loin was sprayed with a mixture of 2% lactic acid and 2% (vol/vol) acetic acid and the corresponding half was used as a control. The strip loins were stored at -1°C for 0, 7, 14, 28, 56, 84, or 112 days and evaluated for chemical, physical, and microbial properties. The internal pH increased significantly (P < 0.05) beginning at day 56 for all products. Vacuum scores and visible purge scores showed that these qualities became less desirable over storage time. There were no significant differences (P > 0.05) for meat color, fat color, or odor over storage time. Acid-treated strip loins had significantly lower (P < 0.05) visible purge scores than control strip loins. Internal and external pH, vacuum, meat color, fat color, and odor were not affected by acid treatment. In a calculation of time-by-treatment interaction (P < 0.05), acid-sprayed strip loins had less percentage of purge than corresponding controls at 56 and 112 days of storage. Water-holding capacity decreased over 84 days of storage. Anaerobes, lactic acid-producing bacteria, and psychrotroph populations increased significantly (P < 0.05) over storage time but anaerobes and lactic acid-producing bacteria were reduced by acid treatment. Acid-sprayed strip loins had significantly lower aerobic (P < 0.05) and psychrotrophic (P < 0.1) populations than controls after 14 days. These data indicate that an acid spray immediately prior to packaging can reduce some species of bacteria without adversely affecting the physical properties of products stored for 112 days at -1°C.

Effects of exogenous porcine somatotropin on the carcass composition, hormonal and metabolic profiles, lipogenic capacity, and binding of insulin to erythrocyte receptors of fast- versus slow-growing swine

Twenty barrows were designated as fast-growing (FG) and their littermates designated as slow-growing (SG) based on birth, weaning, and 56-d weight. Half of each group received 70 micrograms of porcine somatotropin (pST)/kg BW daily beginning at 40 kg BW. At 60 and 105 kg BW, blood was collected every .5 h for 12 h beginning 1 h before pST injection, fat biopsies were taken for in vitro lipogenic activity, and insulin erythrocytes were isolated for receptor binding. Swine treated with pST had elevated ADG (.95 vs .88 kg/d; P < .1) and reduced days to slaughter (61 vs 67; P < .1). The pST-treated pigs had less average backfat (2.73 vs 3.96 cm; P < .01), larger longissimus muscle areas (32.3 vs 28.2 cm2; P < .05), and a higher percentage of muscle (56.3 vs 50.3%; P < .01) than control pigs. Exogenous pST increased protein (17.4 vs 13.2%; P < .05) and decreased fat (22.9 vs 37.1%; P < .05). The FG pigs had higher ADG (.98 vs .86 kg/d; P < .01) and required fewer days to slaughter (57 vs 71; P < .01) than SG pigs. Administration of pST increased (P < .01) average pST levels (1.7 vs 14.0 ng/mL) in FG and SG pigs at 60 kg BW. At 105 kg BW, pST was higher (P < .01) in pST-FG than in pST-SG swine (46.0 vs 19.3 ng/mL) but was not different between FG and SG control swine (1.9 vs 1.8 ng/mL). Administration of pST increased concentrations of IGF-I (510.0 vs 160.0 ng/mL) and nonesterified fatty acids (182 vs 109 muEq/L, P < .01) in FG and SG swine. Over sample periods and growth rates, pST reduced (P < .05) CO2 production and lipid synthesis (.345 and 1.85 vs .575 and 2.71 mumol of glucose incorporated.g-1.2 h-1). At 60 kg BW, FG swine had less (P < .01) CO2 production and lipid synthesis (.299 and 1.83 vs .921 and 3.61 mumol.g-1.2 h-1) than did SG swine. Exogenous pST increased (P < .05) binding to insulin erythrocyte receptors (7.25 vs 6.34%).

Prediction of carcass characteristics by real-time ultrasound in barrows and gilts slaughtered at three weights

The carcass characteristics of 27 market barrows and 27 market gilts were evaluated at various times (n = 8) with real-time ultrasound (Aloka 210 DX) from approximately 20 kg until slaughter at three end points. The pigs were randomly assigned to slaughter weight groups of 91, 104.5, and 118 kg at weaning time. Correlations were determined over slaughter weight group and sex, and the accuracies of ultrasound measurements were also evaluated. The regressions of ultrasound 10th-rib fat and ultrasound longissimus muscle area on live weight were also developed. Correlations between actual and ultrasound-measured last-rib fat, 10th-rib fat, and longissimus muscle area were high (r = .91, .63, and .53, respectively; P less than .01). The accuracy of ultrasound longissimus muscle area prediction was lower for 118-kg pigs than for the two lighter groups, whereas the accuracy for prediction of last-rib fat was lower for 91-kg pigs than for the two heavier groups, as indicated by higher absolute differences (P less than .05). Last-rib fat and longissimus muscle area tended to be overestimated and 10th-rib fat tended to be underestimated by real-time ultrasound. Prediction of last-rib fat by ultrasound was more accurate for gilts than for barrows, as indicated by a lower absolute difference (P less than .05).